Jezar's 'How to Use a Compressor'

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This article was written by Jezar at Dreampoint but no longer appears on his site. This is one of many copies scattered around the Internet

--Mark 11:44, 26 November 2005 (GMT)

                         === How To Use a Compressor By Jezar at Dreampoint ===

People are frequently asking how to use a compressor. Here is a little article I have written to explain how you go about it.

Introduction

Most effects processors are fairly simple to use; plug in an equaliser (for example), twiddle the controls, and listen to the output, and you pretty much know what you're doing, and all you need is some experience behind you.

Compressors don't fall into this category. Plug them in and listen. What's it doing? Unless someone has told you, then you probably won't know. Play with the controls. What do they do? Don't know either. What do the indicators mean? Difficult to tell. It's all a bit frustrating really...

Unfortunately you need to be *told* what a compressor does. Furthermore - even after you know what it does - someone needs to explain why the things that it does are considered useful. You won't figure it out for yourself.

Normally - for non-technical people - the explanations of what a compressor does, are so bewildering that they end up even more confused than they were before: "xDBs in, equals yDBs out, over zDb threshold, according to this graph" etc. etc.

Fortunately, I have a friend who explains it very well, and very succinctly:

"What does a compressor do, Alan?" "It makes the loud bits quieter." "I see... But surely if it just makes the loud bits quieter, can't you then turn EVERYTHING right up, and make get everything really, REALLY loud?"

"Exactly."

So there you go. Simple isn't it? A compressor just makes the loud bits quieter, allowing you to crank everything up to maximum volume. But under what situations would this be useful?

Firstly, there's the obvious application of making your CDs sound as loud as possible. This trend is starting to get a bit silly, and is beginning to prevent people from producing albums of good dynamic range. Nevertheless, if you master a rock or pop album with no compression at all, then the chances are it will sound pitifully quiet compared to the rest of the CDs in peoples record collections. It will probably sound like it has been severely under-recorded. Compression lets you get a much higher average level onto the CD without affecting the music too much.

A very practical application of compression is in live PA setups such as a rock concert. There is a danger that very, very loud sounds will blow up the loudspeakers as well as risking serious hearing damage for those near the stage. The solution is to put a compressor in place. This makes the loud bits - and in this case only the very loudest of the loud bits - quieter, so as to avoid damage to equipment (and people). Such hard compression of only the very top peaks of music, is called "limiting", and is so useful that many compressors have a "limiting" function in addition to normal compresson, and so you will have to read the manual if you want to use this feature in addition to using the compressor for additional "normal" compression.

Another example is that many vocalists have poor microphone technique. When they sing quietly, they sing *far* too quietly. When they sing loudly, they are *way* too loud. A compressor can reduce the "dynamic range" of the vocalist to a more managable level, which is why a compressor is sometimes called a "Dynamics Processor".

Bass guitar is another instrument which can be hard to play consistently throughout a song. Any minor errors in the bass guitarists playing can leave "holes" in the song where the bass seems to disappear. A compressor can help keep the performance at a consistent level.

There are obviously many other instruments and sounds that could benefit from compression at some time.

So, as you can see, there are many applications for a compressor. Basically, in any situation where sound volume levels are getting out of control, a compressor can be used to "tame" the extremes of volume and keep it within a reasonable range, entirely according to your needs. Obviously a very powerful